Means for prevention of weakening propeller-shafts by electrolysis.



PATENTED MAY 5, 1903.

. A. "A, KNUDSON. I MEANS FOR PREVENTION OF WEAKENING PROPELLER SHAPTSBY ELECTROLYSIS.

APPLICATION FILED APR. 5, 19oz.

E0 MODEL.

THE mmms warm to vnoTmumQ, WASHINGTON, u c.

Witnesses ADOLPHUS A. KNUDSON, OF BROOKLYN,

Patented May '5, i903.

FFICE.

ATENT NEW YORK.

MEANS FOR PREVENTION OF WEAKENING PROPELLER-SHAFTS BY ELECTROLYSIS.

SPECIFICATION forming part of Letters Patent N 0. 727,382, dated May 5,1903.

Application filed April 5, 1902. -i 1N0.10l,586. (N0 model.)

iron or steel, hereinafter termed steel -are placed in close proximityto each other and immersed in sea-water, or seawater is allowed to flowor penetrate between them, galvanic action or electrolysis will result,causing a disintegration or red uctionin weight of the electropositivemetal. In such cases where the respective metals are steel and bronze,for example, thesteel being electropositive to the bronze, the two arechemically acted upon by the sea-water and a current of electricityleaves the electropositive metal for the negative metal. In conformitywith a law of electrical action wherever currents leave a metal undersuch conditions or under conditions similar to those above describedsuch metal is more or less reduced and weakened. In the construction ofmodern war-ships and ships of the merchant marine this action has beenrecognized as the cause in many instances of the weakening of what istermed the tail-shaft, which carries the screw-propeller, and as theexplanation of accidents to the tail-shaft resulting in the loss of thepropeller and the serious delay of the vessel. The action in this caseis due to the employment of one or more liners, of bronze, upon thetail-shaft, of steel, and the penetration of the sea-water between theshaft and the respective liners and its chemical and electric contactwith the electrically-opposite metals or alloys-that is to say, withmetals of different polarity. Such liners are commonly shrunk upon theshaft, and thus made secure thereon with or without the aid of rivetsextending through the walls of the shaft into the customary longitudinalbore. Whether or not such rivets are employed it is impracticable torender the j ointsbetween the shaft and the respective linersWater-tight, and the sea-water eventually penetrates between the twometals, as above stated, and produces the electrolytic action. Theelectrolytic action in this case manifests itself in various Ways; butmainly and most seriously in what is termed annular nicking, where theends of the respective liners are opposed to the shaft. Such'ann ularnickin g obviously invites cracks and frequently results in a break in ashaft and the loss of the propeller. By such an ac cident the lives ofthe passengers are placed in great danger and serious financial loss tothe owners of the ship is involved. Various means have been proposed forpreventing such weakening of propeller-shafts by electrolysis; but sofar as I am advised the difficulty has heretofore remained Without aknown remedy that is effective.

The object of the present invention is to render impossible the galvanicaction of electrolysis above described, and thus to prevent so weakeningthe propeller-shaft.

The invention consists in certain novel combinations of partshereinafter set forth and claimed.

'A sheet of drawings accompanies this speci fication as part thereof.

Figure 1 of the drawings represents a longitudinal section through thestern-bearing of a modern vessel, exposing to view the tailshaft. Fig. 2represents a cross-section, on a larger scale, at A B, Fig. 1. 7

Like reference-letters indicate like parts in both figures.

The framework or at the keel of the ship is provided with the customarystern tube or casing 12, of cast-iron, provided internally with bearingsc, of lignum-vitae. Within said bearings liners d are secured upon thetail-shaft e in any known or improved manner. Instead of making suchliners d of a metal or alloy of different electric polarity from thetail-shaft e, as heretofore, I make them of. a metal or alloy that is ofthe same or substantially the same polarity as the tail-shaft, and'thusprevent any galvanic action or effect thereon of sea-water andeffectively protect the shaft against electrolysis.

With a tail-shaft e of nickel-steel, which is a preferred materialtherefor, I make the liners d of wrought-iron containing a sufficientproportion of nickel to render it of the same or substantially the samepolarity as nickelsteel.

For the purposes of the present invention the tail-shaft 6 will in allcases be of the metal or alloy known as nickel-steel; but theWrought-iron of the liners d may be alloyed -with other metals, providedthe liners are of the same or substantially the same polarity as thetail-shaft.

Having thus described said improvement, I claim as my invention anddesire to patent under this specificationl. The combination of apropeller-shaft of nickel-steel and liners secured upon said shaft andconstructed of an alloy the basis of which

